I'm very doubtful that any way of doing this will be easier than connecting the display to a Pi Zero and writing a little code to implement some sort of protocol for your MicroPython board to tell the Pi what to display - but then I don't really see why it would make sense to attach a keyboard, mouse and screen to a MicroPython board so I will assume you have your reasons

If you don't want to have a USB hub dangling off your USB host shield you could get a keyboard with a built-in hub and plug the mouse into that. Or you can still get PS/2 keyboards and mice, so you could have a go at implementing a PS/2 interface - I don't know if that's feasible using interrupts directly on the MicroPython board or if you'd need another chip to convert it to a friendlier format. A PICAXE-08M2 can easily be programmed to read keypresses from a PS/2 keyboard and output them via serial, I2C etc.